High level waste is stabilized with Joule-heated vitrification melter in Japan. Platinum group metals (PGMs), which are Ru, Rh and Pd included in high level waste, form micrometer-sized dense particles in molten glass and increase viscosity and electric conductivity of glass. Distribution of PGM particles is one of the key factors in the operation of the vitrification melter, however, it is hard to measure PGM particle concentration directly because of radioactive environment. In this study, we present a conceptual system for PGM concentration estimation by non-contact monitoring of glass flow from outlet nozzle. This system consists of two parts, which are glass viscosity estimation by glass flow profile and temperature measurement of glass flow by non-contact devices (Fig. 1 a). Measured temperature and estimated viscosity of glass are associated with PGM concentration by temperature-viscosity curves of molten glass (Fig. 1 b).
For this purpose, we carried out two examinations. One is numerical experiences of glass flow from outlet nozzle of melter to correlate flow glass profiles with boundary conditions and glass properties. The other is application of radiation thermometer to glass flow to construct a non-contact measurement device. The results showed the feasibility of the proposed estimation method after integration of numerical experiences and accuracy improvement of radiation thermometer.
This work was carried out as a part of the basic research programs of vitrification technology for waste volume reduction（JPJ010599）supported by the Ministry of Economy, Trade and Industry, Japan.